Natural abundance of δ 15N confirms insectivorous habit of Roridula gorgonias, despite it having no proteolytic enzymes

Abstract

Natural abundance values of plant δ 15N give an indication as to the source of nitrogen. In particular, carnivorous plants are expected to be relatively enriched due to trophic enrichment of their prey. Values of δ 15N for adult Roridula gorgonias (mean + 3.02 ‰) are 4-9 ‰ greater than co-occurring non-carnivorous plant species and 5.24‰ greater than juvenile R. gorgonias plants. They are also 3.5-4.26‰ greater than co-occurring Drosera species which, being sundews, are considered to be carnivorous. These high levels of δ 15N in adult plants are best explained as being due to access to trophically enriched N from insects. As is the case for other carnivorous plants, leaves and stems of R. gorgonias are highly ultraviolet reflective and are therefore probably attractive to potential insect prey. This is further support for this plant species being insectivorous.